Optimal Tax Policy under Habit Formation and Capital Utilization. Goncalo Monteiro State University of New York at Buffalo, NY 14260 Adam Cook State University of New York at Buffalo, NY 14260 Sanjoy Dey State University of New York at Buffalo, NY 14260 Abstract Our objective is to investigate how the combination of habit formation with endogenous capital utilization decisions affects the process of economic growth. We find that in the presence of positive productivity growth, habit formation in consumption reduces the rate of capital utilization while increasing the long run stock of capital. We show in the Chamley-Judd result of zero income capital taxation is robust to the presence of endogenous capital utilization. The result even extends to the short-run as long as there are no depreciation allowances, but breaks if those are present. Our policy simulations show that steady state level of capital utilization is not affected by changes in income tax, but its reduced on impact to accommodate for the constancy of capital stock Our numerical simulations also show important differences in the time adjustment followed by key variables, as a response to tax policy. Keywords: habit formation; capital utilization; optimal taxation; Economic growth; user cost. JEL classification: D91, E21, O41 1. Introduction Recently, Solow(2005) advocated for the considerations of demand-side and supply-side interaction in the study of economic growth. According to Solow: “…some sort of endogenous knitting-together of the [short-run] fluctuations ad growth contexts is needed, and not only for the sake of neatness: the short-run and its uncertainties affect the long-run through the volume of investment … and the growth forces in the economy probably influence the frequency and amplitude of short-run fluctuations.” The standard Ramsey growth model is certainly at odds with this argument. On the preference (demand-side) it assumes agent’s utility functions, at any point in time, depend only upon contemporaneous variables such as current consumption (sometimes leisure). On the production side (supply-side) it generally assumes production depend on physical capital 9sometimes labor or human capital) with full utilization of the installed capital. Therefore, in order to address Solow’s suggestion we need to depart from the standard Ramsey model. The current work, tries to account for the interaction between demand-side and supplyside forces by departing from the Ramsey model in two distinct ways. On the preference side we recognize the limitations of this time-separable specification of utility have become increasingly recognized, and thus allow current utility to depend not only on current consumption, but also on past consumption levels, which provide a benchmark against which current consumption can be assessed. This type of model are generally called models of habit-formation and were first introduced by Ryder and Heal (1973), and recently have been applied to a variety of issues, incuding but not limited to: asset pricing (Constantinides, 1990, Campbell and Cochrane, 1999), consumption behavior (Osborn, 1988, Fearson and Constantinides, 1991, Dynan, 2000), shortrun macroeconomic stabilization (Ljundqvist and Uhlig, 2000, Fuhrer, 2000), exchange rate behavior (Mansoorian, 1988) and economic growth (Carroll, Overland, and Weil, 1997, 2000, Fuhrer Alvarez-Cuadrado, Monteiro, and Turnovsky, 2004, Alonso-Carrera, Caballé, Raurich, 2005, Turnovsky and Monteiro, 2007). On the production side we use the Keynes’ (1936) idea that firms increase the intensity of capital usage during a certain working period, and this leads to accelerated depreciation, thus affecting future capital accumulation. Contrary to what happens with the habit formation, the idea of higher wear and tear on equipment resulting from higher utilization rate, has received little interest by economic growth theory contrasting with what happens in the business cycle literature. An explanation for this behavior may be that while it seems natural to include capital utilization as an optimal decision variable to explain cyclical variation in output, it is less evident that the underutilization of capital would persist in the long-run, and thus play a key role in explaining economic growth. . Dalgaard (2003), however, shows, non-negligible long-run productivity differences can arise from plausible changes in the capital utilization rate, thus making this inclusion in the economic growth relevant. A few notable exceptions to the neglect mentioned above are: Licandro, Puch and RuizTamarit (2001), who analyze the equilibrium dynamics of an optimal growth model with endogenous depreciation, variable capital utilization and maintenance costs and they conclude that in the long-run capital is optimally underutilized and maintenance activities are optimally undertaken. Rumbos and Auernheimer (2001), introduce a variable rate of capital utilization into a modified Ramsey model, whereas Dalgaard (2003) introduces endogenous capital utilization decisions into the standard neoclassical model. Both conclude that this reduces the speed of convergence. Marquez and Ruiz-Tamarit (2004) extend the AK model by introducing adjustment and maintenance costs. The most recent and “extensive” work belongs to Chatterjee (2005), which accounts for the optimal choice of capital utilization in a growth model employing a general production function (that accounts for the Ramsey, the AK and the semi-endogenous growth models), and shows that capital utilization plays a crucial role slowing down the speed of convergence. In spite of the empirical support for capital utilization and habit formation, the combination of these two concepts has only been done (to our knowledge) by Marc-André Letendre(2004) in the very different context of a small open economy model calibrated to replicate the Canadian economy. It is our view that combining this two ideas is in line with Solow(2005) suggestion, but more importantly considering endogenous capital utilization decisions under time separable utility may yield misleading conclusions if in fact preferences are characterized by a high degree of complementarity between consumption at successive moments, as the empirical evidence suggests [see Fuhrer (2000)]. On the other hand, it is also true that considering habit formation in consumption, while ignoring capital utilization decisions, may yield misleading conclusions if in fact the rate of capital utilization falls substantially below the full utilization rate. Of the studies cited, our analysis is closest to Chatterjee (2005)whose conclusion is that incorporating capital utilization decision into the Ramsey model helps to resolve the discrepancy between theory predictions and actual speed of convergence. Our paper objectives are a bit broader than the speed of convergence debate; the goal is to investigate the effects combining endogenous capital utilization with habit formation in consumption, on the predictions of the Ramsey growth model. Therefore, we expand the Ramsey growth model to account for the presence of a reference benchmark on consumption, as well as endogenous capital utilization decisions. In particular, we consider the implications of habit formation on the optimal decisions of capital utilization using a one sector neoclassical growth model in which labor experiences positive productivity growth. In addition, we proceed to do some optimal tax policy analysis as well as some numerical simulations of the effect of tax policy instruments. It is worth mentioning that the model is general enough to allow for a comparison of our results not only with the capital utilization model, but also with the model of habit formation and the traditional neoclassical model. Therefore, we extend this comparison whenever it is relevant. There are several key results that we wish to stress at the outset: the first and possibly most general result is that the steady state of capital utilization and depreciation are only affected by the weight of habits in the utility function, in the presence of labor productivity growth. In the presence of labor productivity growth, the presence of habits raises (reduces) the steady state of capital (rate of capital utilization) relative to the time separable preferences case, presented in Chatterjee (2005). A possible explanation could be that agents do not like negative consumption shocks, and their effect increases with the weight ( ) assigned to the consumption reference. To guard against these shocks, a more addicted (higher gamma) agent will lower the rate of his firm's capital utilization in order to lower the rate of capital depreciation and increase the pool of available capital just in case he experiences a negative shock and must consume more of his capital stock to maintain his habit. Second, the introduction of endogenous capital utilization has implications for the optimal tax analysis. An immediate implication is, we must distinguish between the intertemporal (on capital accumulation) and the intratemporal (on capital utilization) effects of optimal tax policy. The Chamley-Judd result of zero long-run optimal income holds even in the presence of depreciation allowances. Third, the Chamley-Judd result fails to hold in the shortrun in the presence of capital depreciation allowances. There are also some important results coming from the tax policy analysis. First, an increase in the income tax rate reduces utilization in the short-run, but has no effect on the longrun. Second, increases in depreciation allowances increase the utilization rate by a larger percentage in the short-run than in the long-run. The intuition is simple and is just a response to the fact that capital cannot adjust in the short-run. The paper is organized as follows. Section 2 lays out the model. Section 3 characterizes the corresponding macroeconomic behavior for the decentralized economy and the cental planner solution is presented in section 4. The optimal tax analysis is conducted in section 5 and we analyze the effects of shocking the economy in section 6. Section 7 concludes, and an appendix provides some technical detail. 2. Model 2.1 Preferences Consider an economy populated by N identical and infinitely lived households that grow at an exogenous rate N N n . At any point in time, agents derive utility from current consumption, Ci and a reference consumption level, H i . The agent’s objective is to maximize the intertemporal iso-elastic utility function: 1 1 0 1 Ci Hi e t dt 1;0 1 (1) the condition 0 1 reflects the presence of non-satiation and this is guaranteed if an increase in a uniformly maintained consumption level increases utility, i.e. UC Ci , Ci U H Ci , Ci 0 . In other words non-satiation is guaranteed if the reference level augments the direct effect of consumption, or, if it is offsetting, it is dominated by the direct effect. Following Ryder and Heal (1973) we assume the agent’s reference stock is an exponentially declining weighted average of his own past levels of consumption, and can be specified by Hi t Ci e t d t 0 (2) Differentiating (2) with respect to time yields the following rate of adjustment for the reference stock, Hi Ci Hi (3) where measures the relative importance of, or the weight assigned to, recent consumption in determining the reference stock. Hence, higher values of lead to lower level of persistence of the reference benchmark in consumption. 2.2 Production On the production side, agents make decisions at two distinct levels. First, and at any instant in time, agents must choose the optimal level of investment, thus determining the flow of capital into the economy. Second, given the level of capital chosen for the economy, agents decide how much to use in production, i.e. it chooses the rate of utilization of the accumulated stock. Therefore, individual output is determined by the flow of services derived from the available level of capital in the economy at a certain time, K is , and the level of inelastically supplied labor, Li . Assuming a Cobb-Douglas production individual output is determined by, Yi ALi K s 1 i (4) where K is uK i represents the fractional flow of capital services used in final good production, and u represents the rate of utilization or the intensity at which the total available stock of capital in the economy is utilized1. In addition, it is also assumed labor productivity grows at the exogenous growth rate, A A g . An immediate implication of introducing capital utilization in the model is that it no longer makes sense to consider, as is traditionally the case, that we have a constant depreciation rate. In other words, it is reasonable to consider that the rate of depreciation is increasing with the rate of utilization, simply because the more intensively the agent utilizes the capital, (i.e. the higher rate of utilization) the higher the wear and tear and thus the higher the rate of depreciation. Therefore, the rate of depreciation will be endogenously determined in the model and will be an increasing function of u, and can be specified as: u du , 1, d 0, 0 u 1 (5) where u 0, u 0 and u u u measures the elasticity of depreciation with respect to the rate of capital utilization. 2.3 Government Whereas in models with full utilization and constant capital depreciation there is no significant difference between allowing the government to tax gross rather than net capital, the same is not true in our model of capital utilization. This happens because endogenizing the capital utilization decision introduces a new distortion on capital income taxation. In models of full capital utilization, agents need only worry about the intertemporal allocation decision, whereas in models of endogenous capital utilization decision agents must also worry about a static decision of how much capital to use at each instant in time given the stock of capital. In other words, by endogenizing capital utilization, capital supply is perfectly elastic with respect to any tax rate both in the long run (dynamic intertemporal margin), as well as the short-run (static intratemporal margin) 1 This definition follows Taubman and Wilkinson (1970), Calvo (1975) and Chatterjee (2005) In light of this, we assume the government levies constant taxes on income, ys , and consumption , c , and permits capital depreciation allowances, d . In addition the government maintains a balanced budget, rebating all taxes revenues and allowances as lump sum transfers: T ys r s uK ws AL cC d u K (6) where r s is the rental rate of capital services, and w s is the effective real wage rate. 3. Macroeconomic Equilibrium: Decentralized case Output can be used for consumption or investment. Thus, the individual in the decentralized economy budget constraint is K i 1 ys r s uKi ws ALi n 1 d u K i 1 c Ci Ti (7) The individual chooses his consumption, the rate of capital utilization, the rate of capital accumulation to maximize (1), subject to the production (4), to the rate of depreciation (5), the accumulation equation (7). If we define c Ci AL , k Ki AL and h H i AL , and let U c, h ch 1 1 , the agent’s optimization problem can be equivalently expressed as: max U c, h e t (8) 0 s.t. k 1 ys r s uk ws n g 1 d u k 1 c c T (9) where 11 g and to simplify the notation, we let U c and U h denote the partial derivatives of U c, h with respect to c and h The optimality conditions for this problem are, U c 1 c 1 r 1 d u s y s (10a) 1 d 1 ys r s u 1 d du n g (10b) (10c) where denotes the agent’s shadow value of capital, together with the transversality condition: lim e t t k t 0 t (10d) The interpretation of the optimality conditions (10a)-(10c) is standards in growth literature. Equation (10a) equates the utility of an additional unit of consumption to the tax adjusted shadow value of capital taking into account that utility depends upon current consumption relative to the benchmark; equation (10b) determines the optimal rate of capital utilization by equating the marginal benefit to marginal cost (in a way this is an intratemporal or static allocation condition). Equation (10c) is the standard intertemporal allocation condition equating the marginal product of capital to the rate of return on consumption. Using the normalized variable definition on the production function (4) and the adjustment for the reference stock (3), yields: y Kis 1 uk 1 (11) h c h gh (12) On the production side, the representative firm takes the effective real wage w s and the rental rate of capital services r s as given, and rents capital and labor services from the representative agent to maximize profits, : Max ALi Li , Ki K s 1 i r s K is ws ALi (13) With the following first order conditions: rs ws Yi 1 ALi K is 1 uk s K i 1 Yi 1 1 ALi Kis uk ALi (13a) (13b) Before we proceed to determine the macroeconomic equilibrium we should point that the proposition presented in Chatterjee2 (2005) still holds here. This proposition states that, as long as the rate of depreciation depends on the intensity at which the available stock of capital in the 2 See section 3.3. page 2101 economy is utilized u , agents will always find it optimal not to use the full amount of capital in the economy, i.e. 0 u 1 . We now proceed to derive the macroeconomic equilibrium. The first step is to replace (13a) into (10b) and solve that for the rate of capital utilization as a function of efficient units of capital and the tax rates, which yields, 1 1 ys 1 1 1 1 u k k Bk 1 d d (14) and the depreciation function (5) becomes, u d Bk 1 (15) 1 1 ys 1 1 . B 1 d d where In addition, substituting (14) in the production function (11) specified in units of efficiency, yields, y f k B k with (16) 11 1 Expressions (14)-(16) are equivalent to the results presented in Chatterjee (2005), if we assume no government involvement, i.e. zero tax rates. This is not surprising, because the reference stock is related to the preference side of the model and not to the production side, and thus does not affect the use capital directly. These expressions show a positive (negative) relationship between the marginal product of capital (aggregate capital stock) and the rate of utilization3. From equation (10.a) we obtain 3 or alternatively the rate of depreciation c C ( h, ) (17a) C h, 2U , with i h, , we have that with i, j c, h and Ci i ij Defining U ij Ch 1 c 0, U ch ; C U cc U cc (17b) Using (17a) and (6) the macroeconomic equilibrium is terms of the canonical system is summarized by expressions (9), (12), (10.c) 1 ys 1 k c h, n g k k B1 1 1 d (18a) h c(h, ) h gh (18b) 1 1 1 B k (18c) g n 1 1 ys (18c) Imposing the stationary conditions, k h 0 on the system (18a)-(18c) we can determine the steady state values, for k , c, and h in the following recursive manner. First, (18c) yields the solution for capital. Second, given k (18a) determines the solution for c . Third, substituting this value of c into (18b) we get the steady state value for h [alternatively (18b) can be used to yield the consumption-habit ratio]. Finally we use expression (10a) to determine the solution for the shadow value of capital, . Letting tildes denote the steady state values, we may summarize these expressions as follows: 1 1 1 ys B1 k g n c B 1 h g 1 1 1 ys 1 1 k n g k 1 d c c g h (19a) (19b) (19c) U c c, h (19d) 1c In addition, using the steady state value of capital (16a) on (14) and (15) the steady state values for the rate of capital utilization and the rate of depreciation are 1 1 g n 11 1 g n u 1 d d 1 1 d d 1 (20a) and 11 1 g n 1 d 1 (20b) The following observations about the steady state can be made: First, we see that in contrast to the steady state level of capital which depends both upon the income tax rate, ys and the rate of depreciation allowance d , the rate of capital utilization depends only on the rate of depreciation allowances. Intuitively, the decision to accumulate capital depends on both the amount of disposable income, as well as the intensity with which it will be used. The two components are affected by different government policies. On the other hand, the decision about the intensity of capital utilization is made taking capital as given, and thus is only affected by the government depreciation allowances. It can easily be shown that, du 0; d d dk 0; d d dk 0 d ys which intuitively can be explained because a rise in income taxation reduces the amount of disposable income and thus reduces investment. The effect of the depreciation allowance on utilization and capital is simple and intuitive to understand. Depreciation allowances lead agents to increase capital utilization because of the tax savings (rebate) resulting from utilization and thus the larger the rebate the larger the incentive to increase utilization. In contrast, and for the exact opposite reason, the incentive to increase utilization detracts agents from capital accumulation. Second, in the absence of productivity growth, g 0 , the steady state values are independent of , the relative weight attributed to habit in the utility. In this case (16c) implies that c h , so that the steady state level of consumption coincides with the steady state reference stock level. In that case (16a) reduces to the standard modified golden rule stock of capital, consistent with the early result of Ryder and Heal (1973), and more recently Alvarez-Cuadrado et al.(2004). Third in the presence of positive productivity growth, g , the steady state values are no longer independent of the relative weight attributed to habit in the utility, .As shown in Wendner (2011) this effect occurs because the elasticity of marginal utility becomes a channel through which a consumption externality affects the steady state equilibrium —even in the absence of elastic labor supply and a consumption–labor tradeoff. Of particular interest to our model is the effect of habit on the steady state level of capital and even more importantly the rate of utilization (similarly rate of depreciation). Using comparative statics we can show that in the presence of non-satiation, 0 1 , and restricting 1, k 0; u 0; 0 meaning that introducing habit formation into the utility function unambiguously increases the equilibrium normalized stock of capital while decreasing the equilibrium rate of capital utilization and depreciation. This is a result of the smoother adjust in consumption that takes place in the presence of a reference benchmark for consumption. An increase in the weight of the reference benchmark requires an increase in capital to maintain the future value of consumption. This positive effect of habits on capital accumulation is a result of the fact that in the presence of positive productivity c h , and the only way to maintain this relationship is by having a higher steady state stock of capital. In other words, given that shocks to consumption are bad, having a higher steady state capital stock hedges against the deleterious effect of a negative production shock. Furthermore, given a fixed level of output and increasing importance of habits, the reference consumption level magnifies the effect of a negative consumption shock, and thus more steady state capital level must accrue to adequately mitigate this “habit risk.” Finally, we look briefly at the effects of the elasticity of depreciation with respect to the rate of capital utilization, , on the steady state values of the rate of depreciation ( ), and on the rate of utilization u . An increase in , decreases the steady state rate of depreciation. Regarding its effect on the steady state rate of utilization, there is no loss of generality, and the analysis is simplified, if we assume g n 0 . With this assumption the steady state rate of capital 1 utilization reduces to u . According to this expression full utilization of capital, d 1 i.e. u 1 , happens when 1 d 4 and when . Given that u is between zero and one we can say there is a “U relationship” between u and . In other words, there is an inflection point, say inf , for which the effect of on u is negative to the left of that point, inf , and positive to the right of that point, inf 5. To consider the transitional dynamics linearize (18) around the steady state. The dynamics can be approximated by the third-order system, presented below: k 0 h 1 2 B k Ch Ch 1 g 0 C k t k C h t h 0 t (21) Economic intuition have us believe that with k and h being sluggish variables while is free to jump instantaneously, the system should have a unique stable adjustment path (i.e. saddle path stability) and thus have two negative and one positive eigenvalues. In what follows, we discuss only the results and relegate the corresponding derivations to the appendix. It can be 4 In page 2013 of Chatterjee (2005) it reads”…as increases above 1 d , u falls below 1…”.There is a typo in this statement; the “cut-off value” is 1 d and not as presented in the paper. 5 For a detailed analytical discussion see Chatterjee (2005) easily verified that the sign of the determinant of the matrix (21) is positive. This, however, is consistent with having either two negative and one positive root, or three positive roots. To ensure the system exhibits saddlepoint behavior requires extra conditions, but in all of our simulations, however, we find that (21) exhibits saddlepoint behavior and we focus our attention on that case, it being the plausible one. 4. Macroeconomic Equilibrium: centrally planned economy In deriving this optimum, the individual agent neglects the externalities present in consumption. As a consequence, the macroeconomic equilibrium generated by the decentralized economy may diverge from the social optimum. In the context of consumption externalities this has been analyzed by Turnovsky and Monteiro (2008) and Liu at al.(2004). The central planner understands that consumption reference stock depends upon the economy-wide average consumption level, [which equals the consumption of the representative agent], and thus internalizes the impact of the agent’s current consumption decision on the future evolution of the reference stock, in accordance with (3). Performing the maximization, the optimality conditions become. The optimality conditions for this problem are, U c 1 uk (22a) d u 1 (22b) 1 u1 k du n g U h g (22c) (22d) where denotes the agent’s shadow value of capital, is the shadow value of the agent’s reference stock, together with the transversality conditions: lim e t 11 g t t k t lim e t 11 g t t h t 0 (22e) The interpretation of the optimality conditions (22a)-(22e) has some important differences from the decentralized economy. First equation (22a) equates the utility of an additional unit of consumption adjusted by its impact on the future reference stock to the shadow value of capital, while equation (22b) determines the optimal rate of capital utilization by equating the marginal benefit to marginal cost. Equation (22c) is the standard intertemporal allocation condition equating the social rate of return to capital to the social of return on consumption. Equation (22d) is an additional intertemporal allocation condition equating the marginal disutility of an additional unit of the reference stock measured in terms of its shadow value to the cost of the reference stock. From equation (22.a) we obtain6 c C ( h, , ) And we define like before Ch U ch ; U cc (23a) C 1 0, C 0 U cc U cc (23b) Using (23a) the macroeconomic equilibrium is terms of the canonical for the central planner is described by 1 1 k B1 k c h, , n g k (24a) h c(h, , ) h gh (24b) 1 1 1 B1 k n g 1 (24c) g U h (24d) 6 Where U ij denote the second order partial derivatives of the utility function with respect to the two arguments For simplicity we use the utility notation instead of the actual results. 1 1 1 where B1 d Imposing the stationary conditions, k h 0 on the system (24a)-(24d) we can determine the central planner's optima for k , c, h and in a similar recursive manner as we did in (19a)-(19c). Letting * denote the optimum values; we summarize these expressions as follows: 1 1 B11 * k g n 1 (24a) 1 * * c* B11 1 k n g k h* g c* c* g h* (24b) (24c) U h c* , h* g (24d) * U c c* , h* * (24e) In addition, using the steady state value of capital (24a) we can derive the steady state values for the rate of capital utilization and the rate of depreciation 1 n 1 g u* d 1 (25a) and n 1 g 1 * (25b) The parallels between these optimum values and (20a)–(20b) for the decentralized economy are clear. Indeed if we eliminate the tax rates, all the expressions remain unchanged. This is not surprising in light of the results obtained in Liu et al.(2004), and Turnovsky et al.(2008), who show that consumption externalities have no effect in the steady state if labor supply is exogenous. To consider the transitional dynamics linearize (23) around the steady state. The dynamics can be approximated by the fourth-order system, presented below: k 0 h B 1 k * 2 * 1 0 Ch C Ch 1 g C 0 0 U hh U hcCh U hcC C k t k * C h t h* 0 t * a44 t * (26) with a44 g U hcC Economic intuition have us believe that with k and h being sluggish variables while and are free to jump instantaneously, the system should have a unique stable adjustment path (i.e. saddle path stable) and thus have two negative and two positive eigenvalues. In what follows we discuss only the results and relegate the corresponding derivations to the appendix. It can be easily verified that the sign of the determinant of the matrix (18) is positive. This, however, is consistent with there being either two negative and two positive roots, four positive, or four negative roots. To ensure the system exhibits saddlepoint behavior requires extra conditions, which turn out to be very simple and weak in nature; namely that the diminishing marginal utilities dominate, i.e. U cc U hc 0 , U hh U hc 0 5. Optimal Tax Policy The objective is to characterize a tax structure such that the decentralized economy mimics the dynamic equilibrium path of the centrally planned economy. In the standard approach, there is no qualitative difference between taxing only the gross rental capital income or to tax rental income net of depreciation. In both cases the optimal policy prescribes zero taxation in the long-run [(Chamley (1986) and Judd, (1985)]. But once capital utilization decisions are endogenized, the optimal taxation policy is sensitive to the way we define taxable income. It is important to remember that, as was shown by Liu et al. (2005), and Turnovsky et al. (2008), in the absence of endogenous labor the long-run solution for the decentralized and the central planner coincide, i.e. the consumption externality does not affect the steady state only the transition. Therefore, it is not surprising that the optimal tax discussion presented here does not depend on the consumption references parameters. In contrast, endogenous utilization decision will play a key role in the determination of the optimal tax policy. For a better comparison with the existing literature it is convenient to consider two possible scenarios. In the first case, the government only levies the income tax, ys because firms are not allowed to deduct capital depreciation. In light of the previous discussion the government taxes income gross of capital depreciation. However, if you read the IRS publication 946, titled how to depreciate properly, we see that real-world tax systems consider some degree of depreciation deductions for tax purposes. Therefore, in the second scenario capital depreciation allowances are possible. An immediate difference between the standard Ramsey model and a model with endogenous utilization is that in the Ramsey model we only need to worry about the effect of taxation on the intertemporal decisions of capital accumulation. In contrast, the endogenization of capital utilization, adds another source of distortion to the agent decisions. Now, and in addition to the intertemporal distortion, the agent must also worry about the static allocation (intratemporal decisions about utilization ) distortion arising from the choice of the rate of utilization. In sum, in the presence of endogenous utilization we must consider not only the long-run analysis, (intertemporal effect on capital accumulation decision), but also the short-run or static effect on capital utilization decision. i) Optimal income tax in the absence of depreciation deductions. Proposition 1: in the absence of capital depreciation allowances, d 0 , the optimal long-run tax rate on capital is zero, ˆys 0 . Therefore, we can say the Chamley-Judd result of zero long-run optimal income tax, holds in the presence of endogenous utilization decisions. Proof: looking at expression (19a) and (24a), and setting d =0, we can see that k k * the result in (24a) 1 1 B11 * k g n 1 1 1 1 with B1 d can be reproduced by the decentralized case (19a) 1 1 1 k g n s y B 1 1 1 1 with B d s y 1 1 If and only if ys 0 In the end, this is to be expected because the endogenization of the utilization decision does not affect the intertemporal margin of capital taxation. Proposition 2: this result of zero long-run income taxation also extends to the short-run income taxation, i.e. ys 0 for all periods of time. Proof: the optimality condition given by expression (22b) implies that 1 uk d u 1 Whereas the intratemporal condition of the decentralized economy, expression (10b) [combined with (13a)], yields 1 1 uk s y d u 1 Replication of the central planner optimal value requires that ys 0 in the short-run too. The explanation for this result relies on the fact that in the presence of endogenous utilization, capital supply is perfectly elastic not only in in the long-run (via investment decisions) but on the short-run as well (via utilization decisions.) Therefore, income taxation produces both a long-run as well as a short-run distortion, which are so large in terms of utility that the optimal tax policy requires ys 0 in both the long and the short-run. ii) Optimal tax policy in the presence of depreciation deductions. The previous result is based on the idea that government taxes capital gross of depreciation. In contrast to the standard neoclassical model where the distinction between gross and net is inconsistent for optimal tax purposes, we can show that the same is not true when utilization decision is endogeneized. In this case the intratemporal utilization decisions create a departure from the traditional optimal tax policy analysis. Proposition 3: in the presence of deductible capital allowances , the optimal long-run taxes should be equal to zero, i.e. ys d 0 . Therefore the Chamley-Judd results of zero long-run income taxation still holds in the presence of depreciation allowances. Proof: this proof is similar to the one for proposition 1 and the only difference is that now we compare directly expression (19a) and (24a), without assuming that d 0 . Proposition 4: The result of zero long-run income taxation does not extend to the shortrun, and to eliminate the short-run distortion the optimal tax rate equals ys d i.e. we must have what is known as full expensing. Proof: combining expression (10b)with (13b) (reproduced here for convenience),yields, 1 1 uk s y and combining with (22b) we get 1 d d u 1 (10b’) ys 1 uk d d u 1 (27) which requires proposition 4, that depreciation allowances equals the rate of income taxation. In the presence of endogenous capital utilization expression (27) and the ensuing there should be no wedge between the marginal user cost of capital and the marginal product of capital services. In other words, looking at expression (10b’), it means that the after tax marginal rate of return of investing in capital must equal the after rebate marginal cost of using capital. In this case the government distorts the intratemporal margin of capital utilization via two different channels: ys i) by taxing income at rate ii) rebating the depreciation of capital utilization at rate d In sum, we saw that in the absence of tax allowances for capital utilization, the ChamleyJudd result of zero optimal income tax, holds for both the short and th long run. In contrast if agents are allowed to use full expensing (i.e. fully deduct capital from rental capital income), then the optimal income tax rate is different from zero in the short-run. It is important to notice that the result of non-zero optimal short-run taxation, only holds in the case of full expensing. If agents were only allowed to deduct a fraction of the depreciation, then the zero short-run optimal income tax would still hold. Intuitively, imagine the depreciation has two components: normal and abnormal7. Assume, for simplicity, that the normal component is the typical constant depreciation rate, and that the abnormal is the depreciation resulting from the intensive utilization. Then if agents can only deduct the normal component, it will be resemble the standard Ramsey case and thus he zero optimal short-run income tax will result. 7 For instance this expression could be expressed as u N u N , with the second term representing the abnormal component. 6. Numerical Analysis To get a better understanding of the implications of combining endogenous capital utilization and habit formation, we calibrate the model and perform some dynamic analysis. Before we proceed it is worth mentioning that, in light of the dynamic analysis performed in Alvarez-Cuadrado et al. (2004), the absence of endogenous labor makes both the external (decentralized solution) and the internal case very similar. Therefore, we ignore the external case and contrast the dynamic behavior of our specification under the habit formation case8, with three other economy specifications that have been widely used in the literature. These models can be seen as special cases of our model which are obtained by considering polar cases of the parameters and , namely: (i) neoclassical growth model9 ( 0, ), (ii) the habit formation case ( ) and (iii) the capital utilization case ( 0 ). Table 1 summarizes the parameters upon which our simulations are based and most of these are standard and non-controversial. In this regard, 0.65 , the rate of time preference 0.03 , the instantaneous intertemporal elasticity of substitution , 1 0.4 , population growth rate n 0.015 and the growth rate of labor productivity g of 2 percent are well documented, and this being a neoclassical model, normalization 1 is unimportant. [INSERT TABLE 1 AROUND HERE] On the preference side, the critical parameters pertain to the relative importance of the reference stock, , the speed with which it is adjusted, . In this regard, we follow AlvarezCuadrado et al. (2004) very closely, thus making it easy to analyze the implications of extending the habit formation model to account for endogenous capital utilization decisions. Therefore, we set 0.5, 0.2 as benchmark values. However, since the information on these parameters is 8 For this section we solve the habit formation case using a budget constraint of the type k 1 ys uk 1 1 c c n g 1 d u k . The solution to this problem is straightforward but is available from the authors on request. It is left out here to save space. 9 Setting 0 the reference stock, H, is irrelevant for utility, in addition when we have full utilization of capital u 1 sparse, we let vary to 0 (conventional case), 0.2, 0.8 (this later case based on the estimates provided by Fuhrer (2000)) and 1. On the production side, different estimates for the elasticity of depreciation with respect to the rate of capital utilization, , can be found in Burnside and Eichenbaum (1996), Finn(1995) and Dalgaard (2003). We consider the benchmark value to be 1.7 , which lies in the middle of its estimated range of 1.4-2. However, in light of the different estimates we let equal 1.4, 1.45, 1.5, 1.56, 1.6 and 2. In this regard, we follow Chatterjee (2005) very closely, thus making it easy to analyze the implications of extending the capital utilization decision model to account for habit formation. Given the lack of empirical estimates for d we set it at 0.3, by following the discussion in Chatterjee’s (2005) footnote 19. The calibration exercise is as follows: for any given value of the model derives an optimum depreciation rate ( ), and we use this value to calibrate the neoclassical and the habit formation growth models. We then compare the speeds of convergence and other relevant equilibrium quantities from the models by varying and . We begin this section by contrasting the steady state of the different models, and then focus on the dynamic response to two fiscal shocks, namely: i) a 10 percent increase in income tax, from 0 to 10% and ii) a 10 percent increase in the rate of tax deduction for depreciation. 6.1. The Steady State Equilibrium. The goal of this section is to contrast the steady state values of consumption and output in different models with our model. This analysis is done assuming the taxes are zero, and since the steady state of these variables does not depend on , we focus on the effects of and . Table 2A-2D reports relative differences in scale-adjusted output and consumption between our model, the habit formation model, the neoclassical model, and the capital utilization model. The relative differences in scale-adjusted quantities are defined as 1 Z Z i , where Z is the equilibrium value for the model of capital utilization with habit formation and Z i corresponds to the value of one of the other three models, namely the habit formation, the neoclassical and the capital utilization. The first thing to notice is that the neoclassical and the habit formation models constantly overstate the steady state equilibrium of output and thus consumption, whereas the capital utilization model always understates the steady state equilibrium of output and consumption. The overall underestimation of the level of output in the capital utilization spans the range of 1 to 10.78 percent for output and 0.6 and 6.42 percent for consumption. This underestimation is increasing in and . For example, when 0.8 [as estimated by Fuhrer (2000)], using the one sector capital utilization model underestimates the value of output between 4.558 and 8.16 percent. [INSERT TABLE 2 AROUND HERE] In the case of habit formation, the differences are the same for output and consumption and range between 10.86, when 0.2 , and 33.75 percent, when 1 . If one were to take the value of 0.5 as used in Alvarez-Cuadrado et al (2004), we see that the steady state is overstated between 14.44 and 29.94 percent, which is quite a significant value. In the neoclassical case the overstatement is smaller than in the habit case ranging between 9.94 and 26 percent for output, and 10 and 30 percent for consumption. In the limit when , capital utilization converges to 1, and depreciation becomes zero, two “groups” are formed. On the one hand we have the “habit formation group”, because our model and the habit formation model converge to the same steady state level of output. On the other hand, we have the “one sector group” with the capital utilization and the neoclassical growth model converging to the same level of output. In this case the “one sector group” underestimates the “habit formation group” by values that range between 2.5 and 14.2 percent, while output underestimates range between 3.5 and 22.6 percent. [INSERT TABLE 3 AROUND HERE] Table 3 looks at the implications of habit formation on the rate of capital utilization and depreciation. The immediate conclusion is the presence of a negative relation between the optimal rate of capital utilization as well as depreciation and the weight of habits in utility, . Additionally and for the range of used in our numerical simulations depreciation and the rate of capital utilization are decreasing in 10. According to the first row of Table 3, when 0 , we see that the optimal capital utilization in the no habit model varies between 84 percent and 56 percent. Introducing habit formation into this model reduces capital utilization by significant amounts, with the values ranging from approximately 4 percent, when 0.2 and 1.4 , and 31 percent when 1 and 1.4 . In sum, Table 2 and 3 highlight the fact that failure to account for the joint effect of two empirical relevant effects, capital utilization and habit formation, may lead to significant misestimation of equilibrium quantities. 6.2.Transitional dynamics. This section compares the implications of combining the optimal decision of capital utilization with habit formation with those obtained under a model of just capital utilization. We do this by looking at the dynamic adjustment of key variables after: i) a 10 percent increase in income tax, from 0 to 10% and ii) a 10 percent increase in the rate of tax deduction for depreciation. To illustrate the key differences we focus on the adjustment of three variables: consumption, the rate of capital utilization and capital. [INSERT TABLE 4A AROUND HERE] Table 4A, summarizes the steady state values of consumption, capital and rate of utilization for the benchmark parameters defined in table 1. According to Table 4A, we see that in a model of capital utilization the steady state values of consumption and capital are only 97.6 and 81.1 percent of the steady state in the model of capital utilization with habit formation. As a result of the underestimation of capital, the former model requires a higher rate of capital utilization which is about 10 percent higher than in the latter. Hence, ignoring the combination of endogenous capital utilization decisions and habit formation in consumption implies the model underestimates consumption and capital, while overestimating the rate of capital utilization. 10 The U relationship mentioned during the model derivations occurs for values of 2 It is important to notice that since the model of capital utilization and our model do not have the same steady state, and thus it is convenient to normalize the results so the graphical interpretation is made easier. Therefore, we plot the variables as a fraction of their initial equilibria. After a shock, the economies converge to a steady state value which can easily be converted into a percentage reflecting how much the new steady state differs from the initial steady state. 6.2.1. 10 percent increase in income tax The first thing to notice is that this type of shock does not have a permanent effect on the optimal rate of capital utilization, see expression (20a)and (25a), but affects the transitional adjustment after the shock, see expression (14). [INSERT TABLE 4B AROUND HERE] From Table 4B, we see that a 10% permanent increase in ys reduces the steady state value of capital by 15% percent in all the models. Consumption, on the other hand, is reduced in the long-run by different amounts for all the models; with the magnitudes reflecting the different forces at play in each model. To better understand the implication of this policy one must consider the short-run impact, because the introduction of endogenous utilization makes capital supply perfectly elastic to the tax increase. In the short-run, however, table 4B illustrates that the combination of habit formation in consumption with capital utilization inhibits the jump in consumption at the time of the shock relative to the models without utilization, and increases it relative to the model without habits. In the models with endogenous utilization, the rise in consumption is accompanied by a fall in the rate of capital utilization of 7.5% . Intuitively, in the absence of utilization decisions, the response to the rise in income tax, must be met exclusively by a rise in consumption; and thus consumption increases by 4.6 and 4.4 percent in the model of habit formation and the Ramsey model respectively. In the presence of utilization decisions, firms immediately reduce utilization and thus consumption rises by less. The combination of demand (habit) and supply (utilization) forces leads to a smaller rise in consumption of 1.25%, which is larger than the 0.2% rise in the case of utilization but no habits. Therefore, as capital accumulation decreases over time, so does consumption, but the small initial gain in the presence of utilization leads to a bigger long-run loss in consumption, relative to the models without utilization decisions. 6.2.2. 10 percent increase in rate of tax deductions for depreciation As shown analytically an increase in the tax allowances for depreciation raises utilization in the long-run. The interesting fact is the overshooting observed in the short-run, with utilization rising on impact by 8.12% against the 6.39% observed in long-run. Intuitively, this is can be seen as a way to accommodate the fact that capital accumulation cannot change in the short-run, thus the answer must come through the service provided. In the long run, capital begins to increase and firms can reduce the utilization, but the tax deductions still leave utilization above the initial value. It is also interesting to notice that the only difference in response between the model of capital utilization and capital utilization with habits, is the short-run impact on consumption. This is a result of the way we introduced the government in the model, that eliminates the depreciation allowance from all parts of the model except B and steady state utilization. In other words, it closely resembles a productivity increase. 7. Conclusion This paper adds endogenous capital utilization decisions and habit formation in consumption into a neoclassical growth model, in order to bring together two empirically relevant components. Our objective is to investigate the tax policy implications of this combination for the steady state, and the transitional dynamics. First, we derive the analytical results for our model and show that in the presence of labor productivity the combination of capital utilization and habit formation reduces the optimal value of capital utilization. On the other hand, in the absence of labor productivity, habits have no effect on capital utilization. Second, our optimal tax results show the Chamley-Judd result of zero long-run optimal income tax, holds in the presence of endogenous utilization decisions, irrespective of looking at the net of gross return on capital. The result, however, only extends to the short-run if there are no depreciation allowances. Our simulations on simple tax policy changes show important differences at different levels between our model and the capital utilization, the neoclassical and the habit formation models. Our results suggest that by ignoring the combination of endogenous capital utilization decisions and habit formation, economic growth models may be understating the magnitude of long-run equilibrium in the case of the capital utilization model, but overstating it in the case of habit formation and the neoclassical model. In addition, this simple tax exercise shows that there are significant differences in combining demand and supply forces. It would be interesting to consider the analysis in a richer environment of, for instance endogenous labor supply or productive government spending In sum, our results reinforce the idea that research on economic growth should pay more attention to the interaction of these two models as a way to analyze the implications of economic policy. Thus, in the future it would be interesting to investigate the consequences of endogenizing labor and analyzing fiscal policy implications. Under this setting, it would also be interesting to consider the potential effects on dynamic scoring Appendix We may write the characteristic equation to (18), namely 1 1 g 0 1 B k 2 0 in the form Ch Ch 1 g C C 0 0 U hh U hcCh U hcC C C 0 0 1 1 g g U hcC (A1) 4 1 3 2 2 3 4 0 (A2) where the solutions, i , i 1,..., 4 , are the eigenvalues. Note that 1 2 3 4 4 (determinant) (A3) 1 2 3 4 1 (trace) (A4) It can be verified that 4 = B1 k 2 ( g )( 1 g ) U cc 0 (A5) and that 1 1 2 3 4 f k (Ch 1) g 1 1 g g U hcC f k 1 1 g (A6) 2 1 1 g 0 Result (A5) is consistent with there being either two negative and two positive roots, four positive or four negative roots. Whereas, result (A6) implies that not all eigenvalues are negative. In addition, Descartes rule of signs in coefficients of (A2) determine the number of positive (unstable) roots. Denote the determinant in (A1) by D say, 1 1 g D 0 B1 k 2 0 Ch Ch 1 g C C C C 0 U hh U hcCh U hcC 0 1 1 g g U hcC to simplify the notation we define 1 1 g Adding row two to row one after multiplying it by 1 , yields D 0 B1 k 2 0 g 1 Ch 1 g 0 U hh U hcCh Ch 1 g ( v) 0 U hh U hcCh C U hcC g 1 B1 k 2 Ch 1 g U hh U hcCh 0 0 C C 0 U hcC g C 0 D1 g 0 C U hcC 0 C D2 g Now evaluate D1 : D1 ( ) ( U hcC ) (Ch 1) g v C [U hh U hcCh ] For notational simplicity let U hhU cc U hc2 U U hh U hcCh 0 U cc Hence D1 ( ) 2 (Ch 1) g g U hcC (Ch 1) g [ g U hcC ] CU ( ) ( ) (Ch 1) g (Ch 1) g 2 ( ) 2 (v ) (Ch 1) g [ (Ch 1) g ] CU D1 4 2 v3 2 (Ch 1) g [ (Ch 1) g ] CU v 2 (Ch 1) g [ (Ch 1) g ] CU v Now evaluate D2 : D2 B1 k 2 g C g U hcC v CU hcC B1 k 2 g C g v B1 k 2 C v 2 v g ( ) Thus, combining terms yields the characteristic equation D 4 2 v3 2v 2 3v B1 k 2 U cc ( g ) g 0 (A7) where 2 2 Ch 1 g [ Ch 1 g ] CU B1 k 2 3 Ch 1 g [ Ch 1 g ] CU B1 k 2 U cc U cc 2 In order to have four positive eigenvalues, Descartes rule of sign would require four sign changes and hence 2 0,3 0 . 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